Variable Cam Timing (VCT) has been used in internal combustion engines to provide valve timing adjustment with the intent to increase combustion efficiency. Consequently, engine's employing VCT can realize increased power output and reduced emissions. However, knock in VCT engines causes noise, vibration, and harshness (NVH) issues. As a result, customers may be dissatisfied with the VCT engine and in some cases complain of the unwanted noise. Such noise may originate within VCT actuators that use a locking pin to lock the rotor inside its housing during engine idle. The knock usually occurs during hot idle when the rotor, due to camshaft torque fluctuation, oscillates within the backlash between the locking pin and the pinhole and hits the housing. The camshaft torque fluctuation and the backlash between the locking pin and the pinhole are the two driving factors that can lead to knock in the cam phaser. In particular, a high speed approach of the rotor toward the housing may result in an impact between the two components, causing a ticking noise.
Attempts have been made to resolve the noise issues in VCT systems by repositioning the pinhole that is engaged by the locking pin in the locked position. The pinhole is repositioned with the goal of preventing direct impact between the vane rotor and the housing of the cam phaser. However, a high speed approach of the locking pin can cause incomplete engagement between the locking pin and the pinhole. Furthermore, slower speed approaches of the locking pins may also fall short of achieving impact avoidance. For example, friction and oil viscosity may cause a locking pin, preloaded by a spring, to not extend at a desired engagement speed. As a result, the vane rotor will bounce against the housing when a locking failure occurs, resulting in noise generation. Additionally, the incomplete engagement between the locking pin and the pinhole puts significant stress on the locking pin, causing deformation and durability issues.
To resolve at least some of the aforementioned problems, the inventors have developed a phase control apparatus for a camshaft. The phase control apparatus includes a locking plate including a drive wheel, a pin recess, and a ramped channel opening into the pin recess, a housing coupled to the locking plate, a vane rotor including a vane and positioned in a hydraulic chamber of the housing, and a locking pin positioned within a bore of the vane and movable into a locked position where the locking pin engages with the pin recess. In this way, the ramped channel can provide more time for the locking pin to extend into an engaged configuration. Consequently, NVH in the phase control apparatus can be diminished, and in some cases avoided. As a result, both the durability of the phase control apparatus and customer satisfaction are increased.
In one example, a thickness of the ramped channel decreases in an arced direction extending away from the pin recess. In this way, the likelihood of engagement between the locking pin and the pin recess can be further increased during high speed approaches of the locking pin, for instance.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.